The Guinea international curled a superb shot past keeper Thomas Kraft to lift Gladbach to 60 points, two ahead of Bayer Leverkusen, who beat already-champions Bayern Munich 2-0 on Saturday.
Gladbach are also just two behind second-placed VfL Wolfsburg, with three matches left to play. Schalke 04 are a distant fifth on 45.
Gladbach took the lead through Max Kruse from close range in the 11th minute but only two minutes later Hertha levelled with Swiss Valentin Stocker’s header after the ball bounced off the bar from a Genki Haraguchi cross.
Gladbach’s Granit Xhaka came close three times in the second half with Hertha boxed deep in their own half but the visitors could not find the winner until Traore released his unstoppable shot from the edge of the box for their sixth win in seven matches.
The top three qualify for the Champions League group stage while the fourth team will need to play a qualifying round.
Hamburg SV’s Gojko Kacar scored a late winner as the former European champions stunned Mainz 2-1 to move away from the relegation zone with their second straight win.
The Serbian midfielder curled home a low drive in the 87th minute. Julian Baumgartlinger’s headed own goal had put Hamburg ahead in the first half before Yunus Malli levelled for the hosts in the 76th minute.
Victory lifted Hamburg, the only team to have played every season in the Bundesliga since its creation in 1963, up to 14th on 31 points, one point above the relegation playoff spot with three games left in the season.
Mainz, who had defender Daniel Brosinski sent off in the 89th minute, lost Colombian Elkin Soto to a serious knee injury after half an hour.
The 34-year-old former Colombia international was stretchered off after he miskicked while Rafael van der Vaart was challenging for the ball.
The club said he had dislocated his knee and likely tore two ligaments as well as his meniscus and would remain in hospital.
The defeat was a bitter blow to Mainz as it all but ended their hopes of playing European football next season and left them 10th in the table on 37 points.
(Reporting by Karolos Grohmann; editing by Toby Davis/Alan Baldwin)